This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. Section 119 from an application for APPARATUS FOR RECEIVING SIGNALS IN A BASE STATION FOR CELLULAR RADIO TELECOMMUNICATION SYSTEM filed earlier in the Korean Industrial Property Office on Jan. 23, 1999 and there duly assigned Serial No. 2065/1999.
1. Field of the Invention
The present invention relates to a cellular radio telecommunication system, and more particularly, a base station having a plurality of subordinate base stations with low capacity (Pico-BTS) for processing the multiple frequency channels.
2. Description of the Related Art
A geographic area served by a cellular mobile communication system is divided into a group of smaller geographic areas or cells, each cell having a base station for providing communication service to a mobile phone or a portable instrument within the cell. Additionally, all the base stations are controlled by a mobile switching center (MSC) to enable the communication between the cells. In the cellular communication system employing the CDMA (Code Division Multiple Access), the signals are sent in the same frequency band simultaneously. Accordingly, the signals are either selected or rejected at the receiver end through the process of recognizing the user-specific signature waveform, which is generated by an assigned spreading code technique. As the process of multiplying the signal by the code sequence causes the power of the transmitted signal to be spread over a wide range of bandwidth, the CDMA is sometimes referred to as spread-spectrum multiple access (SSMA). Moreover, the frequency management scheme, which is a necessary feature of the FDMA (Frequency Division Multiple Access), is eliminated in the CDMA system. Accordingly, in the CDMA system, when the user of a mobile terminal wishes to access a communication channel, the mobile terminal is assigned with a code and the communication signal is immediately transmitted, instead of being stored until a frequency slot becomes available for the transmission as in the FDMA system.
Although a base station can serve a number of subscribers with a single frequency channel in the CDMA system, the system needs to be provided with additional frequency channels as the number of subscribers exceeds the channel capacity. In order to employ the multiple frequency channels, the base station must be provided with an MCPA (Multi Carrier Power Amplifier) or MCC (Multi Channel Combiner). Yet, these components increase the size of the base station. For this reason, the cell that has been served by a single base station having a low capacity is equipped with additional subordinate base stations to provide the multiple frequency channels in the system. However, as the base station with a low capacity is provided with a transmission-reception antenna and an exclusive reception antenna in order to achieve the reception diversity, each respective subordinate base station requires another set of the transmission-reception antenna and the exclusive reception antenna, as shown in FIG. 1. Thus, the expansion of the base stations incorporating these antennas to accommodate the multiple frequency channels is very costly.
FIG. 1 illustrates the conventional base station employing the multiple frequency channels having the first through the fourth subordinate base stations (110, 160, 170 and 180) to support the first through the fourth frequency channels, respectively. Each subordinate base station includes a transmission-reception antenna (112, 161, 171 or 181); an exclusive reception antenna (114, 162, 172 or 182); a transmitter (130, 164, 174 or 184); a main receiver (140, 165, 175 or 185); a subordinate receiver (150, 166, 176 or 186); and, a duplexer (120, 163, 173 or 183) connecting the antennas (112 and 114), (161 and 162), (171 and 172), or (181 and 182) with the transmitter, and the main and subordinate receivers. Thus, the conventional cellular system requires each additional subordinate base station to be equipped with a separate set of the transmission-reception antenna and the exclusive reception antenna 114, 162, 172 or 182 which increase the manufacturing cost.
It is an object of the present invention to provide an apparatus and method for a base station of the CDMA communication system to increase the number of subordinate base stations to accommodate the multiple frequency channels without incorporating additional exclusive reception antennas.
According to an embodiment of the present invention, an apparatus for receiving signals in a base station of a CDMA communication system includes a first and a second subordinate base station (Pico-BTS) with a low capacity, each including a transmission-reception antenna; a duplexer connected to the antenna; a transmitter for transmitting the signal to the antenna through the duplexer; a main receiver for receiving the signal from the antenna through the duplexer; and, an auxiliary receiver, wherein the main receiver of the first and the second Pico-BTSs divides the signal from the antenna into two subsets of signals, one of the signal is received by the main receiver and the other is delivered to the auxiliary receiver of the other Pico-BTS via external port.
The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of preferred embodiments as illustrated in the accompanying drawings. The drawings are not necessarily drawn to scale, with the emphasis placed upon illustrating the principles of the invention.